In the electrical arts, various types of connectors are utilized for a wide variety of applications. Particularly in the professional audio field, XLR connectors are currently the industry-standard connector. XLR connectors are available in either male or female types and may be used to connect three conductive wires attached to contact areas on the connector with a complementary XLR connector. Each of the three wires may conduct an electric signal, for example, the three wires may provide HIGH, LOW and SHIELD signals to an attached device.
In many instances, although a device is connected to the XLR connector, the XLR connector itself remains unattached from a corresponding, matable connector. In such cases, the three lines connected to the device remain open. This may lead to the introduction of unwanted noise in the attached device. Such noise may be reduced or eliminated in different ways. For instance, if the input from the connector to the device is coupled to an adjustable input amplifier, the amplifier may simply be turned down. Alternatively, a so-called terminating connector may be attached to the connector which is in use. The terminating connector shorts two of the lines together thereby forming a closed circuit. For example, in the audio field, it is typical to short pin #3 with pin #2.
Noise may arise from a failure to properly terminate the signal lines coupled to an attached device. According to a conventional technique, this noise is eliminated by coupling the open signal line to ground with a resistor having an impedance that matches the impedance of the line. For a typical cable, a 600.OMEGA. resistor is used. Thus, if a line having an active signal is connected to a first XLR connector which in turn is matably attached to a second XLR connector, the line will usually be terminated on a printed circuit board by a matched resistor coupled to ground. However, when the first XLR connector is disconnected from the second XLR connector, the lines coupled to the first XLR connector will no longer be properly terminated. A resistor may be attached to connect the signal line to ground, but this involves soldering a resistor to the line each time the XLR is disconnected. Therefore, conventional solutions to the aforementioned problems are not time-efficient in that they require the operator actively to connect a terminator, to turn down amplification or to attach an external resistor.
Moreover, apart from resulting noise, conventional arrangements do not provide an input to the attached device which indicates that the signal lines to the XLR connector are open. Thus, it is necessary for the user to physically inspect the attached lines to ensure that each-XLR connector is attached as desired, thereby resulting in added burden.
Accordingly, there is a need to provide improved XLR connectors which are self-terminating. That is, there is a need to provide an XLR connector which properly terminates otherwise open signal lines when the XLR connector is unattached to another device, but permits the lines to transmit signals in a normal fashion when the XLR connector couples two devices together. There is a related need to provide an XLR connector which automatically indicates that it is not connected to a corresponding XLR connector.